The overall objective of the proposed research is to characterize the endocrine profile of the known or putative hormonal determinants of male sexual behavior during a crucial prenatal time period in the sexual differentiation of the brain. Exposure of pregnant rats of environmental stress inhibits the masculinization and defeminization of sexual behavior normally occurring in the male offspring of such rats. This appears to be due to suppression of testosterone (T) secretion by the testes of these males on day 18 of gestation. The working hypothesis to be evaluated is that this surge in testosterone is induces by luteinizing hormone (LH) released from the fetal pituitary gland, perhaps in response to secretion of hypothalamic gonadotropin-releasing hormone (GnRH). Environmental stress may act by causing release of fetal pituitary Beta-endorphin, which inhibits the GnRH-LH-T axis, disrupting the precise synchrony between prenatal testosterone secretion and central nervous system development required for sexual differentiation of the brain. Pituitary levels of gonadotropins, prolactin, adrenocorticotropin and Beta-endorphin and hypothalamic levels of GnRH will be assessed throughout the last week in gestation in both stressed and control fetuses, with particular emphasis on the detection of sex differences during this crucial period. A major objective will be the development of computerized quantitative image analysis and microspectrophotometry interfaced with immunocyto-chemistry for quantitative analysis of specifically detected hormone in its site of production. Such quantitative immunocytochemical techniques will be used to determine which pituitary and hypothalamic hormones are altered by prenatal stress treatment.